1220
J. Chem. Eng. Data 2002, 47, 1220-1221
Solid-Liquid Equilibria of Terephthalaldehydic Acid in Different Solvents Dian-Qing Li,* David G. Evans, and Xue Duan Key Laboratory of Science and Technology of Controllable Chemical Reactions, Ministry of Education, Beijing University of Chemical Technology, Beijing 100029, China
Solubilities of terephthalaldehydic acid in water, acetic acid, chloroform, N, N-dimethylformamide, and N-methyl-2-pyrrolidone were determined by a static analytical method at temperatures ranging from 293.15 K to 371.15 K at atmospheric pressure. The Buchowski equation was used to correlate the solubility data with standard deviations in the range 0.006-3.438 g of terephthalaldehydic acid/100 g of solvent.
Introduction
Table 1. Solubilities of Terephthalaldehydic Acid in Different Solvents
As one of the most important aromatic compounds, terephthalic acid is widely used in organic synthesis, particularly in the polyester industry. During the manufacture of terephthalic acid by oxidation of p-xylene, many undesired compounds are formed, including terephthalaldehydic acid, which is a major component of the byproducts. To purify terephthalic acid using simple methods and to separate terephthalaldehydic acid from the reaction mixture, measurement of systemic and comprehensive solubility data of terephthalaldehydic acid in different solvents is needed. The solubilities of terephthalaldehydic acid in N-methyl2-pyrrolidone measured by the synthetic method have been reported in a previous paper;1 solubilities of terephthalaldehydic acid in water and in acetic acid with a mass fraction purity of 0.980, measured at temperatures above 397.2 K, have been reported,2 but these solubility data are not accurate and have insufficient points for practical use. In this work we report solubilities of terephthalaldehydic acid in water, acetic acid, chloroform, N, N-dimethylformamide, and N-methyl-2-pyrrolidone in the temperature range from 293.15 K to 371.15 K at atmospheric pressure. Experimental Section Chemicals. Water used in the experiments was doubledistilled. Acetic acid, chloroform, N,N-dimethylformamide, and N-methyl-2-pyrrolidone were obtained from Shanghai Chemical Reagent Co. and had mass fraction purities of 0.995, 0.990, 0.990, and 0.990, respectively. Terephthalaldehydic acid had a mass fraction purity of 0.998, which was obtained by purifying the commercial product that had a stated mass fraction purity of 0.980. First, terephthalaldehydic acid was dissolved in 10 wt % sodium hydroxide solution. Next, concentration and crystallization were conducted three times to remove the impurities. Then, acidification, washing, and recrystallization in water were carried out to obtain the purified terephthalaldehydic acid. The purity of this aromatic acid compound was analyzed with a high performance liquid chromatograph (LC-10A, Shimadzu). The melting point of terephthalaldehydic acid measured with a NETZSCH STA449C differential scanning calorimeter was 522.8 K and compares with the literature value 520.2 K.3 * To whom correspondence should be addressed. E-mail: Dellsson@ 371.net. Fax: 0086-10-64425385.
T K
S
Sc
g‚(100 g)-1 g‚(100 g)-1
T K
S
Sc
g‚(100 g)-1 g‚(100 g)-1
293.15 298.15 303.15 308.15 313.15 318.15 323.15 328.15 333.15
0.035 0.041 0.053 0.065 0.078 0.098 0.121 0.147 0.183
Water 0.025 338.15 0.034 343.15 0.044 348.15 0.058 353.15 0.076 358.15 0.098 363.15 0.125 368.15 0.159 371.15 0.200
0.229 0.287 0.351 0.437 0.543 0.687 0.865 1.005
0.251 0.312 0.387 0.476 0.583 0.709 0.860 0.963
293.15 298.15 303.15 308.15 313.15 318.15 323.15 328.15 333.15
0.246 0.279 0.316 0.360 0.425 0.511 0.615 0.764 0.926
Acetic Acid 0.164 338.15 0.211 343.15 0.270 348.15 0.342 353.15 0.431 358.15 0.538 363.15 0.668 368.15 0.825 370.65 1.011
1.124 1.366 1.688 2.035 2.463 2.983 3.661 4.155
1.233 1.495 1.803 2.165 2.587 3.079 3.650 3.968
293.15 298.15 303.15 308.15 313.15
0.104 0.118 0.135 0.156 0.183
Chloroform 0.096 318.15 0.114 323.15 0.136 328.15 0.160 332.15 0.188
0.212 0.247 0.293 0.339
0.219 0.255 0.295 0.331
298.15 303.15 308.15 313.15 318.15 323.15 328.15 333.15
54.473 55.729 57.500 59.159 60.736 62.682 64.904 66.911
N,N-Dimethylformamide 50.146 338.15 69.132 52.148 343.15 71.239 54.243 348.15 73.796 56.437 353.15 76.092 58.739 358.15 78.544 61.157 363.15 80.879 63.698 368.15 83.699 66.384 370.35 85.172
69.194 72.172 75.320 78.653 82.189 85.946 89.947 91.790
293.15 298.15 303.15 308.15 313.15 318.15
16.885 19.681 22.892 26.980 31.242 36.013
N-Methyl-2-pyrrolidone 16.387 323.15 41.458 19.427 328.15 48.249 22.911 333.15 55.678 26.888 338.15 64.571 31.410 341.75 72.030 36.532
42.318 48.831 56.146 64.339 70.830
Procedure. Solubilities were measured by the static analytical method.4-6 Excess solute and solvent were placed in a jacketed glass bottle. The temperature was maintained within (0.05 K of the desired temperature with a thermoelectric controlling system (type 501, Shanghai Scientific Instruments). Continuous stirring was carried out for several days with a magnetic bar. Attainment of equilib-
10.1021/je020039e CCC: $22.00 © 2002 American Chemical Society Published on Web 07/10/2002
Journal of Chemical and Engineering Data, Vol. 47, No. 5, 2002 1221 done are polar solvents, terephthalaldehydic acid has larger solubilities in these two solvents than in the other three. Buchowski and co-workers8 developed an equation to deal with systems in which solutes exhibit self-association effects. In fact, this equation is also applicable to most solid-liquid equilibrium systems giving excellent correlation results without considering the activity coefficients of components. The Buchowski equation is given by eq 1,
ln[1 + 100λMsolute/(SMsolvent)]sat ) λh(T-1 - Tm-1) (1)
Figure 1. Solubility of terephthalaldehydic acid in N-methyl-2pyrrolidone: O, previous work;1 9, this work; s, the values calculated by eq 1. Table 2. Parameters for Correlation Equations of Different Solvents solvent water acetic acid chloroform N,N-dimethylformamide N-methyl-2-pyrrolidone
λ
h/K
0.05911 85611.42 0.49649 8912.83 0.07003 43160.69 2.879 × 10-8 2842.26 8.68477 337.94
where λ and h are two parameters, T is the absolute temperature, Tm is the melting point of the solute, S stands for the solubility in grams of solute/100 grams of solvent, and Msolute and Msolvent are the molecular weight of solute and solvent, respectively. The parameter h is related to the enthalpy of solution per mole of solute with units of K, and λ is identified as the approximate mean size of multimer molecules of the solute. The solubility data were correlated with eq 1, and the calculated solubilities Sc are listed in Table 1 for comparison with the experimental values. The values of the two parameters λ and h together with the root-mean-square deviations (RMSDs) are listed in Table 2. The RMSD is defined as
σx/g‚(100 g)-1 0.022 0.093 0.006 3.438 0.557
rium was verified by repetitive measurements during the following several days until the results were reproducible within 0.5%. With the exception of the system terephthalaldehydic acid + acetic acid, compositions of saturated solutions were determined by titration with standard sodium hydroxide solution using phenolphthalein as indicator. As for the system terephthalaldehydic acid + acetic acid, the compositions of saturated solutions were determined by a mass analytical method, in which the amount of terephthalaldehydic acid in the weighed solution was determined by mass after drying in vacuo at 50 °C for more than 6 h. To test the uncertainty of the measurements, one other experiment was done in which the solubility of phthalic acid in water was determined. The experimental value differed from the literature value by less than 1%.7 The solubilities of terephthalaldehydic acid in the five solvents are listed in Table 1. Values represent the average of three or four independent determinations. In this work the estimated uncertainty of solubility was less than 0.001 g of terephthalaldehydic acid/100 g of solvent. Results and Discussion Measured solubilities of terephthalaldehydic acid in N-methyl-2-pyrrolidone are shown in Figure 1 together with our previous measurements using the synthetic method.1 It is clear from Figure 1 that solubility data measured using the two methods are in close agreement. Because N,N-dimethylformamide and N-methyl-2-pyrroli-
σx )
[
1
n
ci
i)1
]
1/2
∑(S n
- S i) 2
(2)
where Sci is the solubility calculated by eq 1 and n is the number of experimental points. From Tables 1 and 2 the calculated solubilities show good agreement with the experimental values. The experimental solubilities and correlation equation in this work can used to improve the design of the terephthalic acid purification process and the separation of terephthalaldehydic acid. Literature Cited (1) Li, D.-Q.; Liu, D.-Z.; Wang, F.-A. Solubilities of Terephthalaldehydic, p-Toluic, Benzoic, Terephthalic, and Isophthalic Acids in N-Methyl-2-pyrrolidone from 295.65 K to 371.35 K. J. Chem. Eng. Data 2001, 46, 172-173. (2) Chen, G.-R. Chinese Encyclopedia of Chemical and Engineering Technology; Chemical Industry Press: Beijing, 1990; Vol. 1. (3) Robert, C. W.; Jeanette, G. G. Handbook of Data on Organic Compounds, 2nd ed.; CRC Press Int.: Boca Raton, FL, 1985; Vol. II. (4) Sugunan, S.; Thomas, B. Salting Coefficients of 2-, 3-, and 4-Methylbenzoic Acids. J. Chem. Eng. Data 1993, 38, 520-521. (5) Powell, J. R.; Coym, K. S.; Acree, W. E., Jr. Solubility of Anthracene in Binary Alcohol + 2-Methoxyethyl Ether Solvent Mixtures. J. Chem. Eng. Data 1997, 42, 395-397. (6) Pribyla, K. J.; Chuca, I.; Van, T. T.; Acree, W. E., Jr. Solubility of Anthracene in Ternary Methyl tert-Butyl Ether + Alcohol + Heptane Solvent Mixtures at 298.15 K. J. Chem. Eng. Data 2000, 45, 533-535. (7) Stephen, H.; Stephen, T. Solubilities of Inorganic and Organic Compounds; Pergamon Press: Oxford, 1963; Vol. 1. (8) Buchowski, H.; Ksiazczak, A.; Pietrzyk, S. Solvent Activity along a Saturation Line and Solubility of Hydrogen-Bonded Solids. J. Phys. Chem. 1980, 84, 975-979.
Received for review February 26, 2002. Accepted May 31, 2002.
JE020039E
